-LRB- CNN -RRB- -- It was just after 5 a.m. on a cold November morning in 2011 when Kenneth Chamberlain Sr. , a 68-year-old former Marine with a severe heart condition , accidentally set off a medical alert pendant .

An ambulance was dispatched to Chamberlain 's White Plains , New York , apartment , though police who respond to such calls as a matter of routine arrived ahead of the emergency medical workers .

Within the hour , Chamberlain , who is black , lay dying -- from two rounds fired into his upper body by a white police officer .

What led to the shooting of Chamberlain is the subject of a grand jury hearing underway this month , and a matter of heated debate between the White Plains Police Department and Chamberlain 's family and friends .

Police say Chamberlain came at them with a butcher knife when they broke down the door after he refused to open it ; the family claims the elderly Chamberlain was unarmed , and that he told police through the closed door that he did not need any assistance .

In wake of the case of Trayvon Martin , the unarmed , black 17-year-old who was shot and killed in Sanford , Florida , by a neighborhood watch volunteer , the Chamberlain case has gained national interest -- and national media attention .

More than 206,000 people have signed an online petition demanding `` Justice for Kenneth Chamberlain Sr. , '' with many signatories drawing similarities between the case and that of Martin .

The petition , started by Chamberlain 's son , Kenneth Jr. , calls for Westchester District Attorney Janet DiFiore to charge the officers involved in the shooting with murder and civil rights violations .

`` I am sorry for your loss . An outrage of the magnitude of Trayvon Martin , '' Karen Goodwin of Dover , New Hampshire , wrote on the petition .

Much of the controversy surrounds audio and video recordings made in the minutes before the November 19 shooting .

The medical alert device recorded much of the conversation between police and Chamberlain , according to Kenneth Chamberlain Jr. , who said authorities played the audio and video for the family in the aftermath of the shooting .

`` You hear one of the officers use expletive and said that he did n't give an F. Used the N-word , '' he said .

Law enforcement sources confirmed to CNN 's Soledad O'Brien that racial slurs are clearly heard on the audio tape .

Chamberlain 's niece , Tonya Greenhill , who lived next door , said she heard police banging on her uncle 's door that morning .

Greenhill , who has been called to testify before the grand jury , said she told police that her uncle accidentally set off his medical alert device and that they should allow his family to talk to him , to calm him down .

`` I continued to hear my uncle begging and pleading to please leave him alone , '' Greenhill told O'Brien .

`` I just keep hearing my uncle respond ` Please leave me alone , go away . I did n't call you . I do n't need your help . ' ''

According to a police report , the officers contend Chamberlain put a hatchet through a gap in the front door as officers were trying to pry it open .

A video tape recorded by a surveillance camera in the hallway outside the apartment , and another recorded by a camera mounted on a Taser -- both shown to the family by the district attorney -- show that he is unarmed , Chamberlain 's son said .

Neither video show the shooting . The video from the Taser cut out after it was used .

Police contend they attempted to subdue Chamberlain first with non-lethal force .

`` The officers first used an electronic Taser , which was discharged , hit the victim , and had no effect . While the officers were retreating , the officers then used a bean bag shotgun , '' said David Chong , a White Plains police spokesman .

When that failed to stop Chamberlain , an officer opened fire .

The officer has been identified as Anthony Carelli .

Chong said his office is cooperating with a grand jury investigation , but would not say whether Carelli continues to be on patrol . Carelli 's lawyers say he is a decorated officer who followed procedures .

`` We trust that the grand jury will rightfully determine that Officer Carelli 's actions , while perhaps not understandable or acceptable to the family members , attorneys and other emissaries of the Chamberlain family , were justified under our laws , '' Carelli 's attorney Andrew C. Quinn told CNN in a written statement .

An autopsy report , obtained by CNN , shows the gunshots hit Chamberlain in the side of the arm , indicating he either was not facing the officers or had turned away .

Westchester County is an affluent suburb north of New York City , though Chamberlain lived in a one-bedroom apartment in a public housing project in White Plains -- a commercial hub of roughly 60,000 .

`` I think that what happened that night is that Mr. Chamberlain happened to live in public housing and we had police officers who gave him a command to open the door and when he did n't acknowledge their command , really became very agitated and angry because he was defying what they asked him to do , '' Chamberlain attorney Randy McLaughlin said on `` AC360 . ''

`` They forgot that they were there to deal with a medical emergency . You have here a 68-year-old man who has served this country in Vietnam for six years , and a 20-year retired member of the Department of Corrections for Westchester County who died , but did n't have to die . ''

The Chamberlains have filed a wrongful death lawsuit against the police department .

The shooting death also prompted Westchester County residents to start a `` Network for Police Accountability , '' which calls on the police department to publicize how and when its officers may use deadly force .

CNN 's Chelsea J. Carter contributed to this report .

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The case is drawing parallels to the shooting of Trayvon Martin

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Kenneth Chamberlain accidentally set off a medical alert device , his family says

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Police say they shot Chamberlain after he came at them with a knife

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The family says video and audio recordings prove he was unarmed